1. Field of the Invention
The present invention relates to an inspection apparatus for human body security inspection, in particular, to a millimeter wave holographic scan imaging apparatus for human body security inspection.
2. Description of the Related Art
The known security inspection apparatus mainly includes a metal detector, a trace detector and a X-ray transmission apparatus. Specifically, a metal detector exhibits sensitivity only on metal material. A trace detector may only detect explosive substance and drugs. A X-ray transmission apparatus may be used to detect material including metal/nonmetal article, explosive substance and drugs etc., and possess a relative high spatial resolution and process in a certain scanning speed. However, due to harm to human body from X-ray photoionizing radiation, a X-ray transmission apparatus is limited on security inspection of human body.
With comparison to the conventional human body inspection system, a millimeter wave inspection imaging technology possesses advantages of penetrating clothing of human body, emitting radiation in small dose to human body, identifying various types of metal and nonmetal contraband articles. With rapid development in millimeter wave technologies and reduction of the cost of millimeter wave devices, millimeter wave inspection apparatus has become more and more popular and plays a more important role in human body security inspection.
The millimeter wave inspection imaging technology can be characterized into two types: passive millimeter wave inspection imaging technology and active millimeter wave inspection imaging technology, wherein the active millimeter wave inspection imaging technology mainly pertains to holographic scan imaging technology.
With regard to active millimeter wave three dimensional holographic scan imaging technology applied to human body security inspection, a cylinder scanning imaging technology is widely used. However, the cylinder scanning imaging technology results in a bulky volume of the apparatus and complicated calculation. Further, the data is theoretically obtained through approximation and accordingly imaging accuracy cannot be ensured. In addition, the cylinder scanning process is performed with vertical antenna arrays, in which the antenna array has a relative big length and rather excessive units, and thus resulting in higher costs. Further, due to its complexity and bigger occupying floor area, the cylinder scanning imaging technology apparatus cannot be used and combined with associated apparatus/devices in existing airport, railway station, customs and other key facilities and spots.
Furthermore, a single-scanning active millimeter wave three dimensional holographic scan imaging apparatus may detect only one side of a human body at one time and thus needs twice scanning so as to achieve a complete inspection on the passenger to be inspected. During twice scanning, the passenger to be inspected has to turn around. The safety inspection process is thus complicated and the speed of the inspection is low.
In order to achieve human body security inspection, it is desirable to provide a millimeter wave holographic scan imaging apparatus, which at least alleviate or eliminate at least one aspect of the above technical problems.